1. Field of the Invention
The present invention relates to a servo control system, and in particular relates to a servo control system having the function of switching memory used for learning control in accordance with a learning period.
2. Description of Related Art
Learning control is used in control of servo motors as a method for accurate motor control by converging a control deviation to zero with respect to a command that is repeated with a predetermined period in a uniform pattern, to improve processing accuracy (for example, Japanese Unexamined Patent Publication (Kokai) No. 4-323706, hereinafter called “Patent Literature 1”). The Patent Literature 1 discloses a foreknowledge repeat control method that enables a convergence of a control deviation to zero, even with respect to a command that is repeated with a predetermined period and contains a component asynchronous to the period.
The learning control includes a time synchronization scheme in which learning is performed with respect to time, and an angle synchronization scheme in which learning is performed with respect to an angle. The learning control requires the allocation of memory used therein. The use of the time synchronization scheme requires delay memory during the time from the start of processing to the end thereof, so that the longer a processing time, the larger the capacity of the delay memory required.
However, the allocation of the required delay memory in a DSP for servo control causes a cost increase with an increase in the capacity of the delay memory. Furthermore, the delay memory is of no use to a normal axis control that does not use the learning control.